Flask



FIG. 1 is a perspective view of a flask showing our new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a top plan view thereof; and,

FIG. 4 is a bottom plan view thereof.

The broken lines in the drawings showing the bottom surface of the flask illustrate the portions of the design that form no part of the claim. 

CLAIM We claim the ornamental design for a flask, as shown and described. 